Box2d Box2d Box2d Box2d Box2d Box2d Box2d Box2d Box2d Box2d center contains contains contains contains deflate deflate deflate deflate deflate empty get get get height inflate inflate inflate inflate inflate intersectWith intersectWith isEmpty isEmptyMinus isEqualTo isIntersect isNormalized isNull kIdentity leftBottom leftTop normalize offset offset offset operator & operator &= operator!= operator* operator* operator*= operator*= operator+ operator+ operator+= operator+= operator- operator- operator-= operator-= operator/ operator/= operator== operator| operator|= rightBottom rightTop scaleBy set set set set set set size swapTopBottom unionWith unionWith unionWith unionWith width xmax xmin ymax ymin

kIdentity() static const Box2d Box2d::kIdentity ( ) static 收缩到原点的空矩形框